The growth of mold, rope, spoilage yeasts and bacteria is a significant problem in edible dough-based products, such as, for example, bread and other baked goods. Such microbial growth significantly reduces the commercial shelf life of the product, increasing the sellers' direct costs due to moldy products that cannot be sold to the consumer and limiting the time available for storage, distribution, display, sale and consumption of the product.
Various preservatives are on the market and are used to inhibit microbial growth so as to extend the shelf-life of edible dough-based products. See, e.g., E. J. Pyler, Baking Science & Technology, Vol. I, p. 227-236 (3rd Ed. 1988). Examples of such preservatives are sodium benzoate, calcium benzoate, potassium benzoate, sodium diacetate, paraben, niacin, calcium acetate, calcium diacetate, sorbic acid, sodium sorbate, calcium sorbate, potassium sorbate, sodium propionate, calcium propionate and potassium propionate. However, when used at concentrations that effectively increase shelf life, preservatives can impart an off-flavor, odor, color and/or texture (e.g., poor crumb structure) to the final product that is undesirable to the consumer. In addition, preservatives can also inhibit yeast cultures which are used to prepare the dough-based product, resulting in manufacturing problems, such as, proofing problems, and increasing costs due to the need to use greater amounts of yeast to offset the yeast inhibition.
Because of the problems associated with the use of preservatives in dough-based products, as a compromise, it has been necessary in the art to employ relatively low concentrations of preservatives, that is, preservative concentrations which provide some anti-mold effect, but do not create unacceptable processing conditions due to yeast dosage requirements or unacceptable impairment to the flavor, odor, color and/or texture of the product. Accordingly, the prior art discloses the use of preservatives, such as, calcium propionate, sodium propionate, sorbic acid, potassium sorbate and sodium benzoate, in dough and baked products at very low concentrations. For example, U.S. Pat. No. 3,900,570 discloses a maximum usage of calcium propionate of 0.25 parts by weight per 100 parts of flour in the finished dough, with the preferred range being about 0.06 to about 0.12 parts. U.S. Pat. No. 4,416,904 discloses concentrations of 0.04% to 0.10% for sodium benzoate, 0.05% to 0.20% for sorbic acid, and 0.4% for calcium propionate. Similarly, E. J. Pyler, Baking Science & Technology, Vol. I, p. 227-236 (3rd Ed. 1988), discloses that calcium propionate is normally used in the amount of 2.5 to 3.5 oz/100 lb flour. More recently, WO 99/08553 discloses that preservatives, such as, sodium and calcium propionate, are typically added to bakery products in small concentrations in the range of 0.1 to 0.625%, calculated on the weight of the flour.
A number of solutions have been proposed to avoid the problems associated with the use of preservatives in edible dough-based products. U.S. Pat. No. 2,997,394, for example, discloses incorporating a preservative into an edible fat having a high melting point, which is then dispersed throughout the dough. By incorporating the preservative into the edible fat composition, it was reported to be possible to use the preservative in the dough in an amount of about 0.025 to 0.2%, the range depending on the particular preservative, while avoiding unacceptable side effects, such as, yeast inhibition.
Similarly, WO 99/08553 discloses encapsulating a preservative, such as, calcium propionate, into a degradable and edible fatty acid substance which is then dispersed in the dough system, and ultimately released. Again, the encapsulation of the preservative is stated to have the benefit of avoiding inhibition of the microbial culture used to prepare the food product. However, yeast inhibition remains a problem with preservative encapsulation technologies, presumably caused by leakage of the preservative from the encapsulation layer into the dough.
U.S. Pat. No. 6,132,786 proposes another solution for obtaining improved mold inhibition without impacting the organoleptic properties of the baked product by using food grade metabolites produced by Propionibacterium sp, instead of traditional preservatives, such as, propionic acid. The metabolites are reported to have a neutral taste, which does not change the flavor of the product, as compared to propionic acid, which is stated to have a distinct unpleasant taste. The metabolites are also stated to not result in deleterious changes in the consistency or structural integrity of the finished or stored baked product. Nevertheless, it has been difficult to obtain effective and uniform mold inhibition using propionibacteria metabolites.
In addition to the incorporation of small concentrations of preservatives into the dough, preservatives have also been applied to the surface of the baked product, that is, to the exterior of the baked product after baking. As with the case of the use of preservatives inside the dough, preservatives have been applied to the surface of the baked product in small amounts.
Hickey, C. S. Bakers Digest, 54 (4), 20 (1980), for example, reported that a spray application of a 1.0 to 1.5% sorbate solution on hot, freshly baked breads, buns and rolls, and English muffins was effective to increase the shelf-life of the products. The surface treatment was reported to result in sorbate residuals equivalent to 0.02% based on flour.
Malkki and Rauha, Bakers Digest 52 (1), 47 (1978), disclose an aerosol method for mold inhibition in which a solution of propionic acid is atomized at a concentration of 15 mg/liter into an aerosol within an enclosed cooling tunnel through which the bread is conveyed. It is reported that the bread will absorb a concentration of 0.05% of the inhibitor in a 2 mm-thick crust.
He and Hoseney, Cereal Chem, 67 (6), 603-606 (1990), disclose spraying of calcium propionate solution on the surface of bread after baking and after cooling the bread for 50 minutes or 10 minutes. The calcium propionate was added in a very small amount (a 0.2% solution).
Although the addition of preservatives to the surface of the products after baking has been proposed as an alternative to adding the preservative into the dough, because the surface of freshly baked products is fragile and easily damaged, the application of preservatives to the surface of freshly baked products is often undesirable because it can result in the formation of stripes, discoloration, and/or breakage of the product. In addition baked products, such as, bread, are also bulky and hard to handle, thus, making it difficult to uniformly and economically apply the preservative to the surface of the baked product after preparation.
Preservatives have also been applied to the dough prior to heating. U.S. Pat. No. 3,021,219, for example, discloses the addition of 0.5% to 10% of the preservative sorbic acid to pan grease to prevent mold growth. Melnick et al., Sorbic Acid as a Fungistat in Bakery Production With Special Emphasis on a Novel Fungistatic Shortening, The Bakers' Digest 46 (1956), discloses the use of a fungistatic shortening containing sorbic acid or propionate, which is applied to the surface of the dough. DaSa, Sorbic Acid: Its Use in Yeast-Raised Baker Products, The Bakers' Digest 50 (1966), discloses dispersing the combination of sorbic acid and calcium propionate in a vegetable oil, which is applied to brown'n serve rolls before baking. The treatment was also combined with the addition of calcium propionate into the dough and by spraying the surface of the rolls after baking.
In addition to the use in preserving food products, non-toxic, food grade preservatives have also been used in pan release compositions in very low amounts for the purpose of preserving the pan release composition. For example, WO 94/22313 discloses the use sorbic acid, acetic acid, phosphoric acid, benzoic acid and propionic acid, in very small amounts as preservatives of the pan release compositions. In particular, WO 94/22313 discloses a pan release composition comprising 0.25% sorbic acid and 0.25% acetic acid, with the percentage of the preservative being based on the percentage of the pan release composition.
In addition to microbial growth, another major factor which impacts the commercial shelf life of the edible dough based products is the softness of the product, which deteriorates during storage in a process commonly referred to as staling. The staling of a dough based product, such as bread, is generally characterized by an increase of the firmness of the crumb, a decrease of the elasticity of the crumb, and changes in the crust, which becomes tough and leathery. Chemical and enzymatic agents have both been used in the industry to retard staling. WO 91/04669, for example, describes the use of a maltogenic alpha-amylase to retard the staling of baked products.